Mangrove forests constitute the most important sink of carbon (C) in the tropics, the conservation of which is an
essential mean in offsetting C emissions and climate change. Mangrove forests are therefore suggested to be an
important component of reducing emissions from deforestation and degradation (REDD+) schemes, which require
scrupulous quantification of ecosystem C storage in order to monitor temporal C sequestration and emissions.
Despite this, proportionally less is known about ecosystem C storage of mangrove forests in Vietnam,
where these systems constitute a large proportion of its coastline. In this study, ecosystemC storage of a tropical
mangrove forest in Mui Ca Mau National Park, Vietnam (CMNP) was quantified by measuring biomass of trees,
roots, and downed woody debris, and sediment organic C and overall depth. Results showed that aboveand
below-ground C stock ranged from 90.2 ± 15.8 to 115.2 ± 19.3 and from 629.0 ± 32.5 to 687.0 ±
29.2 MgC ha−1, respectively. The combination of the above- and below-ground C stocks resulted in a high ecosystemC
storage,which ranged from719.2±38.0 to 802.1±12.3MgC ha−1, and slightly increased fromfringe
toward interior forest. The 13,400 ha of mangrove forests in the CMNPwere estimated to store 10.3 (±0.8) × 106
Mgof C,which is equivalent to 38.0 (±3.0)× 106 Mgof CO2e. The present results suggest that the conservation of
mangrove forest is needed to increase ecosystem C storage and to offset C emissions at the regional scale.